MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (PRAPIROON) WARNING NR 06// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 22W (PRAPIROON), LOCATED APPROXIMATELY 585 NM SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS DEEP CONVECTIVE BANDING STEADILY DEVELOPING ALONG THE SOUTHERN HALF OF THE SYSTEM. A 081453Z OSCAT PASS AND A PREVIOUS 081236Z ASCAT PASS BOTH INDICATED THE LOW LEVEL CIRCULATION CENTER (LLCC) IS LOCATED SLIGHTLY SOUTH OF THE CENTRAL DEEP CONVECTION. THE CURRENT POSITION TAKES THIS INTO ACCOUNT AND IS BASED ON THE OSCAT PASS AND THE FIX FROM PGTW. THE CURRENT INTENSITY IS BASED ON A CONSOLIDATION OF DVORAK FIXES RANGING FROM 55 TO 65 KNOTS FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES GOOD RADIAL OUTFLOW ASSOCIATED WITH A POINT SOURCE ANTICYCLONE DEVELOPING OVER THE LLCC IN A LOW VERTICAL WIND SHEAR (VWS) ENVIRONMENT (05 TO 10 KNOTS). TS 22W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A MID TO UPPER LEVEL SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS PRAPIROON IS FORECAST TO CONTINUE ON A GENERAL WESTWARD TRACK FOR THE NEXT 12 HOURS BUT WILL START MOVING MORE NORTHWARD AS IT REACHES THE WESTERN EXTENT OF THE STR, WHICH WILL BEGIN TO ERODE AS A SHORTWAVE TROUGH OUT OF EASTERN CHINA DIGS TO THE NORTH OF THE SYSTEM. THE TRACK SPEEDS WILL SLOW AS THE STRENGTH OF THE STR DIMINISHES. BETWEEN TAU 48 AND 72 TS 22W WILL TRANSITION TO A NORTHWARD TRACK AROUND THE WESTERN EXTENT OF THE STR. FAVORABLE UPPER LEVEL AND LOW LEVEL ENVIRONMENTS WILL ALLOW TS 22W TO INTENSIFY THROUGH TAU 72. C. IN THE EXTENDED TAUS, TS 22W IS FORECAST TO TRACK NORTHEASTWARD AS A BUILDING NEAR EQUATORIAL RIDGE LINKS WITH THE STR CAUSING THE STR TO REORIENT NORTHEAST TO SOUTHWEST. A SLIGHT DECREASE IN SEA SURFACE TEMPERATURES AND A SLIGHT INCREASE IN VWS WILL SLIGHTLY WEAKEN THE SYSTEM IN THE EXTENDED TAUS. HOWEVER, THE ENVIRONMENT WILL REMAIN FAVORABLE FOR THE SUSTAINMENT OF THE SYSTEM BEYOND THE FORECAST PERIOD. MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT ON THE RECURVATURE OF THE SYSTEM, BUT VARIES WIDELY IN THE TIMING AND SPEED. THE CURRENT FORECAST IS WEST OF THE CONSENSUS AND FOLLOWS MORE CLOSELY WITH EMCF AND GFS. NGPS, WBAR, EGRR, AND GFDN RECURVE THE SYSTEM MORE QUICKLY (WITHIN THE NEXT 12 TO 24 HOURS). BASED ON THE CURRENT TRACK SPEED AND DIRECTION, AN EARLY SHIFT NORTHWARD SEEMS UNLIKELY. THE CONFIDENCE IN THE FORECAST REMAINS LOW, BASED ON THE WIDE VARIATION IN MODEL GUIDANCE.// NNNN NNNN